Electroacoustic apparatus



July 2, 1940. E. STEFFENS 2,206,517

' ELECTROACOUSTIC APPARATUS Filed Dec. 29, 1958 INVENTOR ATTO R N EY Patented July 2, 1940 ELECTROACOUSTIC APPARATUS Eugen Stefi'ens, Berlin-Siemensstadt, Germany,

assignor to Fides Gesellschaft fiir die Verwaltung und Verwertung von gewerblichen Schutzrechten mit beschrinkter 'Haftung,

Berlin, Germany, a corporation of Germany Application December 29, 1938, Serial No. 248,363 In Germany September 21, 1938 3 Claims.

forming the elastic rim. On the other hand,.

however, the mounting of such rim can not be dispensed with if undistorted operation of the diaphragm is to be insured.

Now, the present invention discloses another method of building diaphragms for electroacoustic apparatus or transducers, such as loudspeakers andthe like, made from fibrous pulp material by immersion or casting. The same so consists in using as the base or support for the fibrous material (such as a cellulosic pulp) a fabric base or' support. Upon this base or support a marginal portion is left uncovered, the

tion and partly in section, while Fig. 2 is a top view thereof, and Fig. 3 is a second modification shown in elevation and partly in section.

Referring now to Fig. 1 diaphragm l consists on the inside of a fabric 2 according to the invention, said fabric serving as a support or base for the layer of fibrous material 3 being applied upon the outside. The sectional view shows with particular clearness that the fibrous deposit does not extend to include the corrugated edge 4 of the diaphragm; hence, the diaphragm edge consists only of the fabric so that it provides an extremely elastic tensioning means for the dia phragm. The diaphragm as to the rest comprises a cylindrical extension 5 for mounting the oscillation or signal-current coil customarily used in electrodynamic loudspeakers.

The diaphragm shown in the modified embodiment of Fig. '3 is designated by 6. In this,

instance the diaphragm has only a fabric support same serving as the elastic supporting rim of the diaphragm, and which, as known in the art, may be corrugated or fluted. The peripheral portion of the fabric support need only be covered during the process of casting or immersion so that no fibrous material will be deposted thereon.

The support or base consists of a gauze network or a similarly constructed'fine-mesh material For example, in making cone-shaped diaphragms a conical porous mold could beused as a support 40 for the stretched fabric, with the fabric being stretched out over the mold.- In this case reducedatmospheri-c pressure could be produced below themold so that the fibrous pulp contained in a receptacle is given a chance to spread 5 over the surface of the fabric as known inthe prior art. r

- In order to understand the invention more clearly several exemplified embodiments thereof and their underlying idea are illustrated in Figs.

1 to 3 of the accompanying drawing, Fig. 1 disclosing a cone diaphragm of the kind adapted to dynamic loudspeaker systems, shown in eleva- 1 extending along its rim or edge portion 8. While the part of the fabric strip 1 located inside the cone-shaped part 6 of the diaphragm is covered with fibrous material, the corrugated edge 9 is again exposed or uncovered, thereby providing 25 the sole means for the elastic securing of the diaphragm. The portion H of the diaphragm which is adjacent the signal-current coil form l0 consists in this case of'fibrous material.

What I claim is: V

1. As an article of manufacture, a diaphragm for an electroacoustic device comprising a conically-shaped fabric support of reticulated fine-v meshed material and a layer of fibrous material cast upon the fabric "support and reinforced thereby.

2. As an article of manufacture, a diaphragm for an electroacoustic device composed of fibrous material reinforced with' a reticulated finemeshed fabric material, the peripheral edge por- 40 tion of said diaphragm being composed solely of the reticulated fine-meshed fabric material.

3. As-anarticleofimanufacture, a diaphragm for an electroacoustic device having a cone portion and a peripheral edge portion, the cone por- 45 tion being composed of fibrous material reinfabric material. 5o EUGEN STEFT'ENS. 

